1. Field of the Invention
The invention relates to a fuel cell system which comprises a fuel cell stack in a manner known per se, wherein air is supplied to the stack (on the cathode side) via an air supply and the waste air is discharged via an air discharge. The starting point for the air supply and the air discharge are an end plate, which closes the stack from the fuel cells, or a distributor plate, which can also be arranged in the center of the fuel cell stack. The entire air circulation is usually designed in such a manner that the fuel cell stack is supplied in an optimum manner with (air) oxygen, so that the reaction of hydrogen with the oxygen takes place there in an optimum manner. Fuel cells are sensitive components. If they are not in operation, the air oxygen can be damaging and especially effect a premature aging of the fuel cell, so that their lifespan is shortened.
2. Description of the Related Art
It is thus obvious to consider to seal the fuel cell when it is not in operation, so that new air oxygen cannot continuously reach the fuel cells. Such a seal has however not been realized up to now. In DE 10 2004 057 140 A1 is only described a valve provided at a side of a fuel cell stack, which serves however for adjusting the oxygen amount during the operation of the fuel cell stack. In order to seal the fuel cell stack with regard to air, locking means could simply be provided outside the fuel cell stack, namely in the air supply and the air discharge. Even if the locking means would be formed in a very simple manner, e.g. as air flaps, there would be the danger of the freezing of the flaps with could ambient temperatures with the consequence connected therewith that the fuel cell system cannot be operated again without further ado.
It is the object of the invention to further develop a fuel cell system in such a manner that a lifespan of the fuel cells is ensured which is as long as possible, without the described disadvantages occurring.